The present invention relates generally to the conversion of methane to C.sub.2 hydrocarbons such as ethane and ethylene by a catalytic oxidation reaction, and more particularly to the catalysts for such a reaction which comprise sodium pyrophosphate over either calcium oxide or gadolinium oxide and which are each capable of providing high yields of ethane and ethylene over relatively long periods of reaction.
Methane is known for its value as a fuel and is a major component of natural gas. While the exploitation of natural gas resources provides a major energy source, the transportation of natural gas in quantity from relatively remote resources requires the use of extensive and sophisticated pipe line systems which present considerable expenditures and give rise to some problems in such transportation of natural gas. In order to reduce these expenditures and problems, investigations have been conducted in an effort to convert the methane in the natural gas to products which can be more readily managed and/or transported than natural gas. The high molecular stability of the methane molecule makes it difficult to convert the methane to other chemical products such as the C.sub.2 hydrocarbons of ethane and ethylene. Previous efforts in this area includes the use of oxidative coupling reactions which have successfully converted the methane to higher C.sub.2 hydrocarbons so as to provide gaseous products which could be readily converted to liquid fuels and/or other desirable chemicals. While various metal oxide catalysts have been used to provide relatively high yields of C.sub.2 hydrocarbons at satisfactory high conversion rates it was found that the reactivity of these previously known catalysts decreased fairly rapidly with time. For example, a lithium/magnesium catalyst which was capable of initially providing a yield of C.sub.2 hydrocarbons ranging from 16 to 19 percent suffered a significant decrease in the order of about 25 percent in this relatively high conversion rate during the first 16 hours of its use.